When binary files are transmitted through Usenet, they must be encoded into a set of printable characters that can be part of messages. There are several methods for encoding these files into characters. The most common method used is called “UUencoding”. This method has been around for a long time, and 90+% of all files sent through Usenet use UUencoding. UUencoding adds about 40% overhead to the size of a posted file.

A second method is called “Base64.” This method of encoding is the most common method for encoding binary files attached to e-mail messages, but it is rarely used for Usenet messages. Base64 encoding adds about 37% overhead to the size of a posted file.

The third, and newest, method for encoding files is called "yEnc". It was invented in 2001. The main advantage of yEnc encoding is that it adds only about 3% overhead to encoded files. Because of this, yEnc encoded file attachments download about 26% faster than UUencoded file attachments. While UUencoding is still far more popular, yEnc is catching on quickly in some binary newsgroups. Frequently, messages with yEnc encoded attachments will have “yEnc” in their subject lines as a warning to people using newsreaders that are unable to decode yEnc attachments. For additional information about yEnc, see http://www.winews.net/yenc/index.htm

News Rover can encode and decode messages using UUencoding, Base64 or yEnc. File decoding is fully automatic: just select a message to download, and News Rover will recognize which type of encoding was used and perform the appropriate decoding. You can select the type of encoding you wish to use for files you post on the Configure/Usenet screen in News Rover.